The flexor digitorum longus performs which action?

The flexor digitorum longus performs which action?

• A. Dorsiflexion
• B. Flexion of Lateral Four Digits
• C. Plantarflexion
• D. Inversion

Answer: (B)

The main idea here is what the flexor digitorum longus does to the toes. Its primary action is curling the lateral four toes by flexing their distal joints, so digits 2–5 are bent at the distal interphalangeal joints. The tendon runs from the posterior tibia, passes behind the medial malleolus, and fans out to insert on the distal phalanges of those toes, which makes this toe flexion its defining function. It can also help plantarflex the foot and aid in inversion, but those roles are secondary to flexing the toes. Dorsiflexion is done mainly by the anterior compartment muscles, plantarflexion mainly by the gastrocnemius and soleus, and inversion is largely the job of the tibialis posterior, so the toe-flexion action best matches the muscle in question.

The main idea here is what the flexor digitorum longus does to the toes. Its primary action is curling the lateral four toes by flexing their distal joints, so digits 2–5 are bent at the distal interphalangeal joints. The tendon runs from the posterior tibia, passes behind the medial malleolus, and fans out to insert on the distal phalanges of those toes, which makes this toe flexion its defining function. It can also help plantarflex the foot and aid in inversion, but those roles are secondary to flexing the toes. Dorsiflexion is done mainly by the anterior compartment muscles, plantarflexion mainly by the gastrocnemius and soleus, and inversion is largely the job of the tibialis posterior, so the toe-flexion action best matches the muscle in question.